This is a double-blind, randomized multi-center phase II/III study trial comparing single versus combination therapy for patients who develop a mutation at Codon 215 of HIV reverse transcriptase. The primary objective of the study is to validate that alteration of codon 215 of reverse transcriptase in plasma in plasma virus proceeds to increase in viral burden as measured in the peripheral blood and decline in CD4 count which have been observed in association with clinical failure on ZDV.